Glass fiber reinforced thermo-setting resin coating and a method for producing the same

ABSTRACT

A glass fiber reinforced thermosetting resin coating on substrate surface, such as the inner surface of a steel pipe, which coating consists of thermosetting resin and a reinforcing amount of glass fibers of sprayable length, and a method of forming such glass fiber reinforced thermosetting resin coating by spraying.

Unite States atent Ishida 1 Mar. 14, 1972 [54] GLASS FIBER REINFORCEDTHERMO- EP, 40 R SETTING RESIN COATING AND A METHOD FOR PRODUCING THESAME [561 References CM [72] Inventor: Masuo Ishida, Kobe, Japan UNITEDSTATES PATENTS 73 A I K I 3,071,162 1/1963 Mick ..138/140 1 2:2 Cmpmm"?Kobe 3,111,440 11/1963 Prentice ...117/104 R x 3,232,812 2/1966 Lorentzet a1..... ..117/97 X [22] Filed: Sept. 2, 1969 Primary ExaminerRalph S.Kendall I21 Appl. NO.. 854,638 Assistant ExaminerE dward G. WhitbyA!t0mey-Roben E. Burns and Emmanuel]. Lohzno 10] Foreign AppliuationPriority Data [57] ABSTRACT Mm U68 Japan 43/65512 A glass fiberreinforced thermosetting resin coating on substrate surface, such as theinner surface of a steel pipe, which [52] 117/104 21 coating consists ofthermosetting resin and a reinforcing 117/161 17/161 117/161 40 amountof glass fibers Of sprayable length, and a method of [51] l t Cl 844dBosh forming such glass fiber reinforced thermosetting resin coatll in bS ra in 58 FieldofSearch ..117/97,126GR,104R,104B, g y p y g Very good 5Fairly good 4 Fair Sproyobil Fairly bad 2 Bad I 1 IO 20 Glass 13 Claims,4 Drawing Figures Gloss fiber length 50 micron I00 m cron 2 lTHCl'Onbubbles a f I 3O 40 fiber con1en1(%) PATENTEUMAR 14 m2 SHEET 1 OF 2 Fig.

F.C.V. Ford Cup(No.4)Vulue,

representing viscosity F.C V.= 50sec F.C.V.= 60sec Gloss fiberlength(micron) 5 4 3 2 I y mm. "m. w m m V W F m B PATENTEDMAR 14 I9723, 549.338

SHEET 2 0F 2 Fig 2 z: 70- c U 0 lb 20 30 Q 4 0 5 0 Gloss fibercontenf(%) Fig, 3 Very good 5 Glass fiber length 51 Fairly good 468:55:32 .9 200m|cron gm: 3 m

Fairly bad 2' Bad I 1 l l l I IO 20 3O 40 Glass fiber content(%) CLASSFIBER REINFORCED THERMO-SETTING RESIN COATING AND A METHOD FOR PRODUCINGTHE SAME This invention relates to a glass fiber reinforcedthermosetting resin coating and a method for producing the coating, andmore particularly to a glass fiber reinforced thermosetting resincoating formed on steel surface and a method for producing such coatingby spraying.

In providing a coating of thermosetting resin on substrate surface, ithas been often practised to laminate a glass fiber layer on the coatingfor reinforcement. According to a known method of such reinforcement, aglass fiber layer is formed by using woven glass fiber cloths, or bydirectly using comparatively long glass fibers of about 3 mm. or more inlength. Such known method for forming a reinforced glass fiber layer istime-consuming. It has been impossible heretofore to provide a coatingof thermosetting resin on a narrowly limited and difficultly accessiblesurface, such as the inner peripheral surface of tubes with acomparatively small diameter.

In other words, for applying a film of thermosetting resin onto a highlyconfined portion of an article, the aforesaid known method usingcomparatively long glass fibers is not practical.

It has been proposed to mix glass fibers with a thermosetting resin,such as polyester, and applying the mixture thus prepared onto a surfaceby spraying for producing a coating. Such spraying method, however, hasdrawback in that spraying nozzles tend to be clogged with the glassfibers, and continuous spraying cannot be effected for an extendedperiod of time.

To facilitate continuous spraying of the mixture of the ther mosettingresin and glass fibers, one may think of using glass fibers which areshort enough to pass through the spraying nozzle without causing anyclogging. Such continuous spraying has not been practised, because shortglass fibers suitable for the spraying were not available on the onehand, and there has been no urgent demand for products made by suchcontinuous spraying process on the other hand. In short, there has notbeen any effective method for the simultaneous spraying of thermosettingresin and glass fiber.

Therefore, an object of the present invention is to provide a novelpractical method of forming a glass fiber reinforced thermosetting resincoating on the surface of steel sheets, steel pipes, ctc., by spraying,which obviates the aforesaid difficulties of known methods. The methodaccording to the present invention is particularly useful, for instance,in providing a coating of reinforced thermosetting resin onto verynarrowly limited surface, such as the inner surface of a small diametertube.

The inventor has found that satisfactory reinforcing effects can beachieved when a coating of thermosetting resin is sprayed in thefollowing manner together with glass fibers. At first, substratesurface, which is to be coated, is preferably cleansed, degreased, andprovided with a primer layer. A mixture is separately prepared whichconsists of a suitable amount of short glass fibers and a thermosettingresin. It is possible to add one or more auxiliary ingredients, e.g., apigment, ag gregates, a catalyzer, and a gelling agent. The mixture thusprepared is sprayed onto the aforesaid substrate surface for producingthe desired glass fiber reinforced thermosetting resin coating.

For a better understanding of the invention, reference is made to theaccompanying drawings, in which:

FIG. I is a graph showing the relation between the length of glassfibers to be added in a spraying mixture and the sprayability of themixture;

FIG. 2 is a graph illustrating the relation between the amount of glassfibers added in the spraying mixture and the hardness of a glass fiberreinforced thermosetting resin coating which is formed by spraying themixture on substrate;

FIG. 3 is a graph showing the relation between the amount of glassfibers added in the spraying mixture and the sprayability ofthe mixture;and

FIG. 4 is a partial sectional view of a steel pipe whose inner surfaceis provided with a glass fiber reinforced thermosetting resin coating,according to the present invention.

The invention will now be described in detail, step by step. Bycleansing and degreasing substrate surface and by applying a primerlayer thereon, the substrate surface is made rustproof and theadhesiveness of the surface to a coating is improved. After a glassfiber reinforced thermosetting resin coating is applied, the primerlayer on the degreased surface acts as a cushion which absorbs thestrain caused by the difference of coefficient of thermal expansionbetween the substrate, such as steel pipe, and the coating made ofthermosetting resin. According to the present invention, however, suchsteps of cleansing, degreasing, and applying a primer layer can bedispensed with, if so desired.

The thermosetting resin usable in the present invention can be anyresins which have thermosetting properties. Some examples of suchthermosetting resins are polyester, epoxy resin, and polyurethane.

The length of glass fibers to be added in the thermosetting resin forthe purpose of reinforcement, according to the present invention, shouldbe determined by tests for each application, so as to meet all thespecific conditions for the application; namely, fulfilling thereinforcing function in the thermosetting resin, being sprayable by aspray gun through a nozzle, and providing satisfactory surface texture.

In case of commercially available glass fibers of 7 micron dia., if eachfiber is extremely short, e.g., shorter than 15 microns, the fibers arenot entwined with each other however great quantity of it is added intothe thermosetting resin. As a result, such too short glass fibers do notcontribute to the reinforcement 0f the resin.

On the other hand, if the individual glass fibers are too long, forinstance several hundred microns long, spray nozzles are easily cloggedby the glass fibers to hamper smooth spraying operation. Furthermore,such long glass fibers become fluffy in the thermosetting resin toroughen the coated surface. Besides, when the glass fibers are too long,the dispersibility of the glass fibers in the thermosetting resin isreduced, and such long glass fibers added in the thermosetting resintend to aggregate by themselves in a pot before spraying and to formbulky lumps in the resin.

FIG. I shows the relation between the length of glass fibers to be addedin the spraying mixture and the sprayability of the mixture, for thecase of the mixtures which consist of polyester acting as thethermosetting resin and 20 percent of glass fibers of 7 micron dia. Itis apparent from FIG. I that the length of glass fibers shouldpreferably be less than 200 microns, although somewhat longer glassfibers can be used with other thermosetting resins at differentconcentrations.

The inventor has confirmed by experiment that as the content of glassfibers in the spraying mixture increases, the curves of FIG. I movetoward left. For instance, if 35 percent of glass fibers are added, thelength of the glass fibers should preferably be less than microns forensuring satisfactory sprayability of the mixture (see FIG. 3).

The amount of glass fibers, which are to be added in the thermosettingresin, should also be controlled. If the quantity of the glass fibers inthe resin is too small, individual glass fibers are not entwined witheach other, even when the glass fibers are very long, e.g., severalhundred microns long. Thus, with such a small quantity of glass fibers,satisfactory reinforcing effects cannot be achieved.

Referring to FIG. 2, which shows the relation between the amount ofglass fibers to be added in the spraying mixture and the Shore hardnessof a coating made by the mixture, it is apparent that at least 10percent of glass fibers should preferably be added in order to achievesatisfactory hardness of the coating. The data of FIG. 2 were obtainedby adding 50 microns long glass fibers of 7 microns dia. in liquidpolyester to prepare spraying mixtures, and spraying the mixture on 1.6mm. thick steel sheets for forming 0.7 mm. thick coatings.

On the other hand, when too much glass fibers are added into thethermosetting resin, the mechanical strength of the resin isdeteriorated, and the viscosity of the mixture of the resin and theglass fiber is increased, regardless of the length of the glass fiberused, so that the workability of the mixture is impaired.

FIG. 3 shows the relation between the amount of glass fibers to be addedin the spraying mixture and the sprayability of the mixture, for thecase of mixtures comprised of polyester acting as a thermosetting resinand 7 microns dia. glass fibers of 50, l00, and 200 microns in length.The viscosity of the mixtures, as determined by Ford Cup No. 4, isadjusted between 50 and 60 seconds. If 40 percent or more of glassfibers is added in the mixture, air bubbles entrapped in small spacesdefined by adjacent glass fibers cannot readily be removed. Besides, theglass fibers tend to settle in the solution. Thus, with such excessiveamount of glass fibers, spraying cannot be effected satisfactorily. Inthe spraying mixtures of FIGS. 2 and 3, 10 to 40 percent of glass fibersare added to liquid polyester.

The diameter of glass fibers usable in the present invention isgenerally restricted to 5 to microns by manufacturing limitations.

The thickness of a coating, which is to be made by spraying according tothe present invention, must be thicker than 0.05 mm. but thinner than 1mm, because any coating thinner than 0.05 mm. does not have the desiredreinforcing effects, while the increase of the coating thickness inexcess of 1 mm. causes various detrimental effects without improving thereinforcing effects.

In a preferred embodiment of the present invention, it is possible toadd into thermosetting resin one or more of suitable auxiliaryingredients, such as a pigment of selected color, a catalyzer, aviscosity-adj usting agent, a gelling agent, and aggregates, such astitanium white and asbestos, together with the glass fibers. The kind ofthe catalyzer, viscosity-adjusting agent and gelling agent, to be usedin the spraying mixture, depends on the kind of the resin used. If thespraying operation can be completed in very short period of time, theaforesaid one or more auxiliary ingredients can be mixed with thethermosetting resin prior to the beginning of the spraying operation. Ifthe spraying operation is expected to last long, the mixture containingsuch auxiliary ingredients may be hardened in a pot before beingsprayed. In order to avoid such prespraying hardening, it is preferableto use a pair of spray guns; namely, one spraying gun connected to a potcontaining a mixture without the gelling agent, and one spraying gunconnected to a pot containing a mixture without the catalyzer, so thatthe two mixtures in the pair of pots can simultaneously be applied tothe substrate surface by the two spraying guns for effecting the mixingof the gelling agent and the catalyzer into the coating during thesolidifying process of the coating on the substrate surface.

As described in the foregoing, according to the present invention, thereis provided a novel method of applying a coat ing of glass fiberreinforced thermosetting resin onto a substrate surface, e.g., steelsurface, by spraying a mixture consisting of the thermosetting resin anda suitable quantity of very short glass fibers. The method according tothe present invention can be used in applying the coating of glass fiberreinforced thermosetting resin onto very narrowly limited surface, suchas the inner surface ofa small diameter steel pipe.

Articles which have the coating of glass fiber reinforced thermosettingresin according to the present invention are provided with not onlyproperties peculiar to the substrate of the articles per se, but alsoexcellent performance characteristics of the thermosetting resin, suchas outstandingly high values of chemical stability, abrasion resistance,heat resistance, and cold resistance.

In FIG. 4, the inner surface of a steel pipe I is degreased andsubjected to chemical conversion treatment to form a conversion coating2 thereon. A primer layer 3 is provided on the conversion coating 2, andthen a desired coating 4 of glass fiber reinforced thermosetting resinis formed on the primer layer 3 by spraying a mixture as describedhereinafter. The mixture to be sprayed for producing the glass fiberreinforced thermosetting resin coating 4 consists of a thermosettingresin and a suitable quantity of very short glass fibers, which arepreferably 15 to 300 microns long. With such mixture of short glassfibers and thermosetting resin, the glass fiber reinforced thermosettingresin coating 4 can be formed much easier than by any other knownmethods which use about 3 mm. long glass fibers. More particularly, theuse of such very short glass fibers enables the spraying of the mixture,which is a highly simplified process for applying such coating onsubstrate surface. If long glass fibers, such as 3 mm. long fibers, areused, it is impossible to use the spraying process, because the longglass fibers tend to clog or plug spray nozzles, as pointed out in theforegoing.

Thus, with the method according to the present invention, the process ofproducing a glass fiber reinforced thermosetting resin coating isgreatly simplified.

It should be noted here that with the introduction of the sprayingprocess, the glass fiber reinforced thermosetting resin coating can nowbe provided on any narrowly confined surface, such as the inner surfaceof very small diameter. Without the use of spraying, application of suchglass fiber reinforced thermosetting resin coating is almost impossible.In other words, satisfactory formation of the aforesaid coating canhardly be effected by brushing.

Furthermore, the aforesaid construction of the coating on the innersurface of the steel pipe 1, which includes the conversion coating 2,the primer layer 3, and the glass fiber reinforced thermosetting resincoating 4, provides greatly improved performance characteristics to thesteel pipe as compared with pipes with known coating, such as steelpipes with vinyl chloride coating. For instance, the steel pipe 1 of thefigure is much better than any known steel pipe with vinyl chloridecoating in heat resistance, cold resistance, and shock resistance.Furthermore, the steel pipe 1, which is coated by the method of thepresent invention, is much cheaper than the known steel pipe withsimilar coating, because the coating process is considerably simplified.

The mixture to be used in the method of the present invention will nowbe described in further detail, by referring to examples.

EXAMPLE I The inner surface of a steel pipe was thoroughly cleansed andprovided with a primer layer. Separately, a mixture was prepared whichwas comprised of 50 percent of polyester, 15 percent of 20 to 30 micronslong glass fibers, and the remainder consisting of a pigment andaggregates. The mixture was applied onto the primer layer on the thuscleansed inner surface of the steel pipe by spraying in order to form a0.7 mm. thick coating. The glass fiber reinforced thermosetting resincoating thus formed had excellent adherence to the steel pipe. Thechemical resistance and the heat resistance of the resin coating provedto be excellent.

EXAMPLE 2 The inner surface of a steel pipe with a mm. inside diameterwas thoroughly cleansed and provided with a primer layer. Separately, aspraying mixture was prepared by adding 20 percent of 50 microns longglass fibers in liquid polyester. The viscosity of the spraying mixture,as measured by Ford Cup No. 4, was adjusted at 50 seconds, by usingstyrene monomer. A 0.5 mm. thick glass fiber reinforced polyestercoating was formed on the inner surface of the steel pipe.

The spraying was carried out smoothly, and the Shore hardness of thecoating on the inner surface of the steel pipe proved to be 70.

EXAMPLE 3 A steel plate was cleansed, and its surface was treated byzinc phosphatizing, and a primer layer was applied thereon.

Separately, a composition was prepared which was comprised of 30 percentof 30 to 100 microns long glass fibers, 45 percent of polyurethane, andthe remainder consisting of a pigment and aggregates. By adding VMCPnaphtha, the viscosity of the composition was adjusted at 100-1 seconds,as measured by Ford Cup No. 4. The composition with the adjustedviscosity was applied onto the steel plate surface by spraying to form a0.67 to 0.70 mm. thick glass fiber reinforced polyurethane coating.

The spraying was carried out very smoothly, and the adherence of theresin coating with the steel plate was excellent. The shock resistanceand the hardness of the resin coated steel plate proved to be excellent.

EXAMPLE 4 The inside surface of a steel pipe of 50 mm. dia. was cleansedand subjected to zinc phosphatizing treatment. Separately, a compositionwas prepared, which consisted of 50 percent of epoxy resin and 50percent of 200 to 300 microns long glass fibers. Acetone was added intothe composition until the viscosity of the acetone solution of thecomposition became 50 seconds, as determined by Ford Cup No. 4. Thesolution of the composition was sprayed onto the inner surface of thesteel pipe to form a 0.55 to 0.60 mm. thick glass reinforced epoxy resincoating. The resin coating proved to be very tough and have excellentheat resistance and chemical resistance.

EXAMPLE 5 The surface of a 1.6 mm. thick steel sheet was thoroughlycleansed and provided with a primer layer. Separately, a sprayingmixture was prepared by adding 10 percent of 200 micron long glassfibers in liquid polyester. The viscosity of the mixture, as measured byFord Cup No. 4, was adjusted at 50 seconds, by adding styrene monomer,and then dyed in blue by adding phthalocyanic blue. A 0.7 mm. thickglass fiber reinforced polyester coating was formed on the steel sheetby spraying the mixture.

The spraying process was carried out smoothly. The Shore hardness of thecoating thus formed proved to be 67. The coated steel sheet was bentwith a radius of curvature, which was three times the thickness of thesheetv It was proved that no cracking and peeling of the coatingoccurred until the bending angle increased to l5or more.

EXAMPLE 6 The inner surface of a steel pipe with a 30 mm. insidediameter was cleansed and provided with a primer layer. Separately, aspraying mixture was prepared by adding 35 percent of 50 microns longglass fibers in liquid polyester. The viscosity of the mixture, asdetermined by Ford Cup No. 4, was adjusted at 60 seconds, by addingstyrene monomer. A 0.7 mm. thick glass fiber reinforced polyestercoating was formed on the steel sheet by spraying the mixture thereon.

The spraying process was carried out smoothly, and the surface of thecoating proved to be sleek.

Although the present invention has been described by referring topreferred embodiment, it should be understood that numerous changes andmodifications are possible without departing from the scope of theinvention, as hereinafter claimed.

lclaim:

l. A method for producing a glass fiber reinforced thermosetting resincoating on a substrate surface, comprising preparing a liquid mixturecomprising a thermosetting resin, and a reinforcing amount of glassfibers of sprayable length, in the range of from 15 to 300 microns inlength and spraying the liquid mixture onto the substrate surface.

2. A glass fiber reinforced thermosetting resin coating on a substratesurface, which comprises a thermosetting resin, a reinforcing amount ofglass fibers of sprayable length, in the range of from 15 to 300 micronsin length said coating being formed on said substrate surface byspraying a liquid mixture of the same thereon.

3. A method for producing a glass fiber reinforced thermosetting resincoating on a substrate surface, comprising preparing a liquid mixturecomprising a thermosetting resin, and a reinforcing amount of from 10 to40 percent of glass fibers of sprayable length, in the range of from 15to 300 microns in length and spraying in liquid mixture onto thesubstrate surface.

4. A glass fiber reinforced thermosetting resin coating on a substratesurface which comprises a thermosetting resin, a reinforcing amount offrom 10 to 40 percent of glass fibers of sprayable length, in the rangeof from 15 to 300 microns in length said coating being formed on saidsubstrate surface by spraying a liquid mixture of the same thereon.

5. A method according to claim 1, characterized in that saidthermosetting resin is selected from the group consisting of polyester,polyurethane, and epoxy.

6. A glass fiber reinforced thermosetting resin coating ac cording toclaim 2, wherein said thermosetting resin is selected from the groupconsisting of polyester, polyurethane, and epoxy.

7v A method according to claim 1, characterized in that said liquidmixture is made by adding 10 to 40 percent of glass fibers in liquidpolyester, the length of said glass fibers being 15 to 200 microns, theviscosity of said liquid mixture, as determined by Ford Cup No.4, beingless than 70 seconds.

8. A glass fiber reinforced thermosetting resin coating according toclaim 2, characterized in that said thermosetting resin is polyester,and said glass fibers are 15 to 200 micron long and contained at a rateof 10 to 40 percent.

9. A steel pipe having a coating on an inner surface thereof, saidcoating consisting of a glass fiber reinforced thermosetting resincoating which contains thermosetting resin and reinforcing amount of 15to 300 micron long glass fibers.

10. A steel pipe according to claim 9, characterized in that saidthermosetting resin is polyester, and said glass fibers are 15 to 200microns in length and contained at a rate of 10 to 40 percent.

11. A steel pipe according to claim 9, wherein said glass fiberreinforced thermosetting resin coating is 0.05 to 1 mm. thick.

12. A method for lining an inner surface of a steel pipe, comprisingcleansing the inner surface, spraying on the inner surface a liquidmixture so as to deposit a resin layer, said liquid mixture consistingof thermosetting resin and a reinforcing amount of 15 to 300 micronslong glass fibers, and heating said layer thus applied on said innersurface.

13. A method for lining an inner surface of a steel pipe, according toclaim 12, characterized in that said liquid mixture is made by adding 10to 40 percent of 15 to 200 microns long glass fibers in liquidpolyester, the viscosity of said liquid mixture, as determined by FordCup No. 4, being less than 70 seconds.

2. A glass fiber reinforced thermosetting resin coating on a substratesurface, which comprises a thermosetting resin, a reinforcing amount ofglass fibers of sprayable length, in the range of from 15 to 300 micronsin length said coating being formed on said substrate surface byspraying a liquid mixture of the same thereon.
 3. A method for producinga glass fiber reinforced thermosetting resin coating on a substratesurface, comprising preparing a liquid mixture comprising athermosetting resin, and a reinforcing amount of from 10 to 40 percentof glass fibers of sprayable length, in the range of from 15 to 300microns in length and spraying in liquid mixture onto the substratesurface.
 4. A glass fiber reinforced thermosetting resin coating on asubstrate surface which comprises a thermosetting resin, a reinforcingamount of from 10 to 40 percent of glass fibers of sprayable length, inthe range of from 15 to 300 microns in length said coating being formedon said substrate surface by spraying a liquid mixture of the samethereon.
 5. A method according to claim 1, characterized in that saidthermosetting resin is selected from the group consisting of polyester,polyurethane, and epoxy.
 6. A glass fiber reinforced thermosetting resincoating according to claim 2, wherein said thermosetting resin isselected from the group consisting of polyester, polyurethane, andepoxy.
 7. A method according to claim 1, characterized in that saidliquid mixture is made by adding 10 to 40 percent of glass fibers inliquid polyester, the length of said glass fibers being 15 to 200microns, the viscosity of said liquid mixture, as determined by Ford CupNo. 4, being less than 70 seconds.
 8. A glass fiber reinforcedthermosetting resin coating according to claim 2, characterized in thatsaid thermosetting resin is polyester, and said glass fibers are 15 to200 micron long and contained at a rate of 10 to 40 percent.
 9. A steelpipe having a coating on an inner surface thereof, said coatingconsisting of a glass fiber reinforced thermosetting resin coating whichcontains thermosetting resin and reinforcing amount of 15 to 300 micronlong glass fibers.
 10. A steel pipe according to claim 9, characterizedin that said thermosetting resin is polyester, and said glass fibers are15 to 200 microns in length and contained at a rate of 10 to 40 percent.11. A steel pipe according to claim 9, wherein said glass fiberreinforced thermosetting resin coating is 0.05 to 1 mm. thick.
 12. Amethod for linIng an inner surface of a steel pipe, comprising cleansingthe inner surface, spraying on the inner surface a liquid mixture so asto deposit a resin layer, said liquid mixture consisting ofthermosetting resin and a reinforcing amount of 15 to 300 microns longglass fibers, and heating said layer thus applied on said inner surface.13. A method for lining an inner surface of a steel pipe, according toclaim 12, characterized in that said liquid mixture is made by adding 10to 40 percent of 15 to 200 microns long glass fibers in liquidpolyester, the viscosity of said liquid mixture, as determined by FordCup No. 4, being less than 70 seconds.